The present invention relates generally to devices for preventing vehicles from passing beyond a predetermined point in a roadway to provide security control and, more particularly, to a roadway barrier that can be selectively actuated to restrict access over a roadway
For many years, a small number of companies have sold vehicle crash barriers primarily designed to thwart deliberate vehicle-based attacks of buildings. These barriers are generally heavy steel structures imbedded in concrete or concrete structures in a road surface that physically obstruct the roadway. These heavy steel structure devices are designed so that a barrier device (usually a steel plate) can be raised or lowered to control the ability of a vehicle to pass through or over the barrier and, thus, gain access to the building being secured. These devices differ from the barriers commonly encountered in parking garages and other public venues, in that they have very high stopping power, for example, preventing a 15,000-pound explosive laden truck traveling at 50 mph from passing beyond the vehicle barrier.
Barriers come in numerous designs, but they can generally be categorized in three conventional types: plate, beam, and bollard. The plate barrier can be oriented to lay relatively flat on the surface of the roadway and be selectively actuated to be angled upwardly upon a perceived threat to form a wedge that restricts passage of a vehicle. The plate barrier is considered to be a permanently installed device as the plate is supported on a concrete encased frame that is buried into the surface of the roadway. A variation of the plate barrier has been introduced recently into the marketplace as a portable barrier. Another variation is to fasten the plate barrier to the roadway, such as with bolts. This barrier device is essentially a plate type barrier that is not imbedded in concrete, but instead can be moved to different locations to accommodate the need for temporary or changing security needs. Since the portable plate barrier is not imbedded in concrete, stopping power is relatively limited.
The beam barrier incorporates a vertically movable beam that is typically pivotally supported at one end of the beam by a steel support that is imbedded in concrete to provide a relatively immovable object and at the opposing end by a similar steel support at the opposing side of the roadway. The beam barrier serves as a movable gate that can be raised vertically (or swung horizontally) to allow vehicles to pass or lowered into engagement with the steel supports at either end of the beam to provide a substantial resistance to the passage of any vehicle. As with the conventional plate barrier, the beam barrier provides a permanent installation and relatively high stopping power. Some beam barriers use bands of elastic material that are contained within the hollow beam and wrapped around the pivot structure for the beam to increase the resistance of the steel beam.
The bollards are typically permanently installed steel or concrete barriers that are typically not selectively movable, although vertical movement could be provided to permit the structure to rise into a passage restrictive position above the surface of the roadway, or be retracted into the ground to permit the passage of vehicles. Generally, bollards are a permanent structure that cannot be made portable without loss of substantial stopping power capabilities.
Historically, vehicle barriers achieved their effectiveness by their mass and by the fact that they were permanently anchored in concrete. The vehicle barrier produced by Nasatka Barrier, Inc. is a beam-type of barrier that utilizes bands in the drop arm (beam) that are utilized to help stop the passage of vehicles. This barrier uses heavy-duty commercial straps or bands (usually nylon) of the kind used to lift large static loads in other commercial applications. While the bands are very strong and have a high stopping power, this beam-type barrier utilizes massive structures to engage each end of the movable beam to resist the impact of the oncoming vehicle. The bands are used to reinforce the drop arm and are anchored at the pivot end of the drop arm.
Conventional barriers have another disadvantage inherent in their designs in that each barrier design requires active mechanical movement of very heavy structures. Heavy steel plates (plate barriers) or heavy cylinders (bollard barriers) have to be raised against gravity in order to stop vehicles. Current vehicle barriers require approximately two seconds for emergency activation from an open position in which the vehicle can pass by the barrier to a deployed position in which a vehicle is prevented from passing by or over the barrier. Activation times for conventional beam barriers and sliding gate barriers are even longer, averaging about ten seconds for barriers that are one traffic lane wide and substantially longer for larger two lane barriers.
In some security barrier installations, a secondary security barrier is installed at a location that is spaced from the primary security barrier to provide a secondary level of protection from the intrusion of vehicles. With such secondary security barriers, the response time is not a critical factor as typically the secondary security barrier is sufficiently spaced from the primary barrier that an operator has ample time to actuate the barrier. However, cost in the manufacture and installation of such secondary security barriers is a significant concern.
Accordingly, it would be desirable to provide an effectively operable, yet low cost vehicle security barrier that can be actuated manually by an operator.